Flush the stdout buffer after compiler runs

Flush the stdout buffer after compiler runs to display all the standard outputs correctly when running in NodeJS spawn. Otherwise it outputs weird result:

When running "compass watch" by Node.js child_process.spawn like this :
```javascript
var compass = require('child_process').spawn('compass', [ 'watch']);
compass.stdout.on('data', function (data) {
	console.log('' + data);
});
```
For the first time it only outputs : ">>> Change detected at 16:34:20 to: XXX", the expected followed lines are missing until another change is made.